Virus Encyclopedia

Conficker.C

Effects

Conficker.C is designed to spread by exploiting a vulnerability in the Windows Server Service which allows remote code execution. It is the vulnerability MS08-067.

Additionally, Conficker.C carries out the following actions:

It checks the system date in the following web addresses:Ask.comGoogle.comBaidu.comYahoo.comW3.organd if the system date is after January 1, 2009, it will attempt to connect to a website in order to download a malicious executable file. The website to which it connects varies depending on the system date.

It disables the following services:- Windows update, disabling the Windows updates.- BITS (Background Intelligent Transfer Service), which is a service to transfer Windows files.- Error reporting service, which allows to send Microsoft information about errors occurring in the operating system, Windows components and programs.

It prevents the user and the computer from connecting to the websites that contain any of the following text strings:ahnlabarcabitavastavgaviraavpbit9cacastlecopscentralcommandcertclamavcomodocomputerassociatescpsecuredefenderdrwebemsisoftesafeesetetrustewidofortinetf-protf-securegdatagrisofthacksofthauriikarusjottik7computingkasperskymalwaremcafeemicrosoftnainetworkassociatesnod32normannortonpandapctoolsprevxquickhealrisingrootkitsanssecurecomputingsophosspamhausspywaresunbeltsymantecthreatexperttrendmicrovetviruswilderssecuritywindowsupdateAs they are security related websites, the antivirus programs could not be updated and the user could not access the information of these pages.

Infection strategy

Conficker.C creates a random DLL in the Windows system directory. This file is created with system, read-only and hidden attributes.

It also creates a file with random name and VMX extension in the folder RECYCLER\%random name% of all the shared and removable drives of the computer. It is copied with system, read-only and hidden attributes. Additionally, it creates an AUTORUN.INF file in these drives. This way, it is run whenever any of them is accessed.

On the other hand, it creates a scheduled task in the folder Tasks of the Windows directory in order to start its execution periodically.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\netsvcs\ParametersServiceDll = %name of the drive%\RECYCLER\%random name%\%random filename%.vmxBy creating these two entries, it is registered as a service.

Conficker.C modifies the following entries from the Windows Registry in order to make its detection more difficult:

Means of transmission

Conficker.C spreads by exploiting the vulnerability called MS08-067, which is a vulnerability in the Windows server service. In order to do so, it sends malformed RPC requests to other computers. If any of them is vulnerable, it will download a copy of the worm to the system.

Additionally, Conficker.C also spreads through the system drives, both shared and removable, making copies of itself in them. It also creates an AUTORUN.INF file in order to be run whenever any of them is accessed.